The development of biological control agents as alternatives to chemical insecticides for the control of important pest species is a subject of increasing interest. Concerns for the environment and exposure of man to harmful substances in air, food and water have stimulated legislation and restrictions regarding the use of chemical pesticides, particularly for pests found in the urban environment. Control of insect pests in urban areas is highly desirable but exposure to chemical pesticides in the household and from lawns and gardens is of great concern to the public. If given a choice, most people would use a non-toxic biological control rather than a toxic chemical to control insects in the urban environment. The problem is that very few biological alternatives to chemical insecticides are available for purchase and use by the public. For most insect pests that need to be controlled in the urban environment (ants, roaches, termites, fleas, wasps, etc.) there is no biological agent available for purchase as a product.
Cockroaches are serious economic pests in urban areas. Because cockroaches are so closely associated with humans and commonly feed on decaying food, crumbs, or scraps, and frequent unsanitary areas such as sewage systems and septic tanks, their presence leads to suspicion of a threat to human health. Pathogenic organisms have been isolated from cockroaches collected in domestic or peridomestic environments; however, the role of cockroaches as vectors of pathogens is controversial. Unlike many blood-feeding arthropods whose feeding behavior results in the direct transmission of pathogens to humans, cockroaches have the potential to transmit pathogens indirectly via contamination of foods or utensils used to prepare food. It has been demonstrated that cockroaches acquire pathogenic bacteria simply by walking over cultures and showed that these pathogens are subsequently transferred to foodstuffs via the normal foraging behavior of the infested cockroaches. Aside from bacterially caused food poisoning and diseases such as typhoid and dysentery, many other human illnesses and diseases associated with microorganisms isolated from cockroaches have been reported. These include paralytic polio, giardiasis, otomycosis, pneumomycosis, and various worms such as hookworm and tapeworm.
Besides the possible role of cockroaches as vectors of pathogenic microorganisms, the mere presence of these insects is known to contribute to human morbidity in other ways. Perhaps the most insidious aspect is the psychological impact of these pests in terms of the anxiety and stress related to infestation, which in some instances can take on pathologic dimensions. Further, defensive secretions among cockroach species may cause burning sensations, vertigo, or nausea in individuals who come into contact with the insects.
Current cockroach control methods in buildings include preventative and corrective approaches. Preventative measures emphasize sanitation to eliminate harborages and food sources, sealing off access routes, and the creation of inhospitable environments by the application of boric acid or sorptive dusts in wall voids during construction (Ebeling, W. [1971] Ann. Rev. Entomol. 16:123-158; Ebeling, W. [1978] Urban Entomology, Berkeley: Univ. Calif. Div. Agric. Sci. 695 pp.). However the implementation of these measures is difficult and thus limits their effectiveness (Thoms, E. M., W. H. Robinson [1987] J. Econ. Entomol. 80:131-135). Corrective measures used to suppress established infestations emphasize the use of insecticide applications. A commonly used technique is to spray insecticides with long residual activity in areas frequented by cockroaches at fixed time intervals (Schal, C., R. L. Hamilton [1990] Ann. Rev. Entomol. 35:521-551). Despite short term suppression of cockroach populations, toxic residues and the development of insecticide resistance (Cochran, D. G. [1989] J. Econ. Entomol. 82:336-341) make total reliance on this technique undesirable. Alternative corrective measures such as the placement of toxic bait traps may provide sufficient control under proper conditions (Thoms & Robinson [1987], supra).
The use of natural enemies for the biological control of cockroaches has been examined to varying degrees. Although traps using biocontrol agents have been proposed, these traps are only as good as the biocontrol agent used. U.S. Pat. Nos. 5,057,315 and 5,057,316. Field releases of parasitoids of the American and brown banded cockroaches resulted in rates of parasitism as high as 95% and has generated some optimism for their potential utilization (Coler, R. R., Van Driesche, R. G., Elkinton, J. S. [1984] Environ. Entomol. 13:603-606; Hagenbuch, B. E., R. S. Patterson, P. G. Koehler [1989] J. Econ. Entomol. 82:90-94). Pathogenic yeasts isolated from laboratory cockroach colonies also have been suggested as possible biological control agents, but more research is required to evaluate their potential (Archbold, E. F., M. K. Rust, D. A. Reierson [1987] J. Med. Entomol. 24:269-272; Archbold, E. F., M. K. Rust, D. A. Reierson, K. D. Atkinson [1986] Environ. Entomol. 15:221-226; Verrett, J. M., K. B. Green, L. M. Gamble, F. C. Crochen [1987] J. Econ. Entomol. 80:1205-1212). Numerous other fungi, bacteria, protozoans, and nematodes have been reported to be associated with cockroaches, but their potential as biological control agents is not significant, or has not been fully evaluated (Roth and Willis [1960] Smithsonian Misc. Coll. Vol. 141; Tsai, Y. H., K. M. Cahill [1970] J. Parasitol. 56:375-377; Zervos, S. [1983] N. Z. J. Zool. 10:329-334; Rahmet-Alla, M., A. F. Rowley [1989] J. Invert. Path. 53:190-196). Thus, there is a significant and long-felt need for a more effective and safe means for controlling cockroaches.
Carpenter ants, Camponotus spp., are distributed throughout North America. Some of the more common and/or studied species include C. modoc in the Pacific northwest, C. clarithorax in southern California, and the C. floridanus in Florida. C. pennsylvanicus, C. noveboracensis, and C. abdominalis, are found in the east (Ebeling, W. [1978] Urban Entomology, Univ. Calif.: Berkeley p. 209-213). Public concern over carpenter ants has been increasing due to the greater probability of structural infestations as suburban developments extend into the forest habitats of the ants.
Pestiferous species of carpenter ants may be considered nuisance pests because of their foraging activity inside homes. More significant damage occurs when carpenter ants extend their nests into sound wood. Nesting sites may be located in live and dead trees, sometimes resulting in damage to shade trees. Nests may also be established in walls and support beams of structures, or in voids within doors, walls, and furniture. Preference for moist or decaying wood has been reported, but nesting sites are not restricted to such areas. Carpenter ant populations develop relatively slowly with colonies of 300-2,000 workers being produced over a 2-year or longer period for various species. The presence of reproductives follows this slow development since their production has been reported only from well established colonies (Hansen, L. D., R. D. Akre [1985] Biology of carpenter ants in Washington state (Hymenoptera: Formicidae: Camponotus), Melanderia 43: 62 pp.; Pricer J. L. [1908] Biol. Bull. 14:177-218). Despite the slow colony growth, large colonies with satellites colonies have been found. Worker movement occurs between the main colony and the satellites, which serve as areas for further brood development and colony expansion (Hansen and Akre [1985], supra).
Current methods for controlling structural infestations of carpenter ants include sanitation of potential and current nest sites, minimizing access to structures (eg. preventing the contact of tree branches with a structure), and the application of insecticides to repel (perimeter spray barriers) and/or eliminate carpenter ants. The use of boric acid dust in dry, wall voids is reported to be effective for up to 20 years (Hansen and Akre, supra).
Recommendations for the chemical control of established structural infestations in the home are often accompanied with warnings of possible hazards to the applicator as well as children and pets. Alternative control methods such as effective biological control agents have not been found (Akre, R. D., L. D. Hansen, A. L. Antonelli [1989] Ext. Bull. Washington State Univ. Coop. Ext. Serv. 1989 rev. no. EB 0818, 6 pp.). A need clearly exists for a safe, effective biological control agent for carpenter ants.
Pharaoh ants, Monomorium pharaonis, have been described as the most persistent and difficult of all our house-infesting ants to control or eradicate (Smith, M. R. [1965] USDA-ARS Tech. Bull. No. 1326, 105 pp.). It is a tropical species which has extended its range to more temperature regions by establishing colonies in heated buildings. Pharaoh ants frequently infests buildings where food is prepared, and have been found to carry pathogenic organisms (Beatson, S. H. [1972] Lancet 1:425-427).
The difficulty in controlling pharaoh ants may be attributed to their inaccessible nesting sites, rapid population growth, and dispersion of colonies. Their small size allows establishment of colonies in any suitable location, including unusual places such as between books and in stored clothing. With multiple queen colonies, and the warm (30° C.), humid (63-80% RH) conditions that favor pharaoh ants, large colonies can develop rapidly. Portions of these large colonies may disperse to form new colonies at any time, probably in response to overcrowding and unfavorable microenvironmental conditions. Unlike other ant species, pharaoh ants do not exhibit intercolony aggression. This permits the adoption of ants from other colonies and may further enhance the establishment of new colonies and reinfestations. Pharaoh ants also forage for food more than 35 m from the nest without distinct trail following, and thus make nests difficult to find and eradicate.
Control methods for pharaoh ants emphasize the use of insect growth regulators (IGR) or toxicants incorporated into baits. Properly implemented bait programs are effective, however it may take over a month to achieve control. Insecticide applications, while fast acting, usually do not eliminate colonies, and may be unacceptable in certain areas where toxic residues are a concern. In addition, insecticide applications are generally not compatible with bait programs. A need exists for safe and effective biological control agents for pharaoh ants.
A United States patent has been granted for a fungus showing high activity against fire ants, U.S. Pat. No. 4,925,663. This isolate, designated Beauveria bassiana isolate No. 447, was deposited in a public repository. No biological activity other than the activity against fire ants had been previously reported for this isolate, nor could activity against other pests be inferred from the mere knowledge that the isolate was active against fire ants. The subject invention concerns the new uses of B. bassiana No. 447.